Elements of Military Art and Science. H. W. Halleck
that they straiten its movements, change the direction of its marches, and force it into detachments; while, on the contrary, they afford all the opposite advantages to the defensive army; they protect its marches, favor its debouches, cover its magazines, its flanks, and its movements, and finally furnish it with a place of refuge in time of need."
These opinions were uttered, be it remembered, long since the period at which modern military quacks date the downfall of fortifications as inland defences, by men, too, who were not engineers, and consequently had no professional predilections in favor of fortifications. The Archduke Charles, as a general, knew no rival but Napoleon, and General Jomini is universally regarded as the first military historian of the age. The truth of their remarks on fortifications is most fully confirmed by the military histories of Germany and France.
For a long period previous to the Thirty Years' War, its strong castles and fortified cities secured the German empire from attacks from abroad, except on its extensive frontier, which was frequently assailed, but no enemy was able to penetrate to the interior till a want of union among its own princes opened its strongholds to the Swedish conqueror; nor then, did the cautious Gustavus Adolphus venture far into its territories till he had obtained possession of all the military works that might endanger his retreat.
Again, in the Seven Years' War, when the French neglected to secure their foothold in Germany, by placing in a state of defence the fortifications that fell into their power, the first defeat rendered their ground untenable, and threw them from the Elbe back upon the Rhine and the Mayne. They afterwards took the precaution to fortify their positions, and to secure their magazines under shelter of strong places, and, consequently, were enabled to maintain themselves in the hostile country till the end of the war, notwithstanding the inefficiency of their generals, the great reverses they sustained in the field, the skill and perseverance of the enemy they were contending with, and the weak and vacillating character of the cabinet that directed them.
But this system of defence was not so carefully maintained in the latter part of the eighteenth century, for at the beginning of the French Revolution, says Jomini, "Germany had too few fortifications; they were generally of a poor character, and improperly located." France, on the contrary, was well fortified: and although without armies, and torn in pieces by domestic factions, (we here use the language of the Archduke,) "she sustained herself against all Europe; and this was because her government, since the reign of Louis XIII., had continually labored to put her frontiers into a defensive condition agreeably to the principles of strategy; starting from such a system for a basis, she subdued every country on the continent that was not thus fortified; and this reason alone will explain how her generals sometimes succeeded in destroying an army, and even an entire state, merely by a strategic success."
This may be illustrated by reference to particular campaigns. In 1792, when the Duke of Brunswick invaded France, she had no armies competent to her defence. Their numbers upon paper were somewhat formidable, it is true, but the license of the Revolution had so loosened the bonds of discipline as to effect an almost complete disorganization. "It seemed, at this period," says the historian, "as if the operations of the French generals were dependent upon the absence of their enemies: the moment they appeared, the operations were precipitately abandoned." But France had on her eastern frontier a triple line of good fortresses, although her miserable soldiery were incapable of properly defending them. The several works of the first and second lines fell, one after another, before the slow operations of a Prussian siege, and the Duke of Brunswick was already advancing upon the third, when Dumourier, with only twenty-five thousand men, threw himself into this line, and by a well-conducted war of positions, placing his raw and unsteady forces behind unassailable intrenchments, succeeded in repelling a disciplined army nearly four times as numerous as his own. Had no other obstacle than the French troops been interposed between Paris and the Prussians, all agree that France must have fallen.
In the campaign, of 1793, the French army in Flanders were beaten in almost every engagement, and their forces reduced to less than one half the number of the allies. The French general turned traitor to his country, and the National Guards deserted their colors and returned to France. The only hope of the Republicans, at this crisis, was Vauban's line of Flemish fortresses. These alone saved France. The strongholds of Lille, Condé, Valenciennes, Quesnoy, Landrecies, &c., held the Austrians in check till the French could raise new forces and reorganize their army. "The important breathing-time which the sieges of these fortresses," says an English historian, "afforded to the French, and the immense advantage which they derived from the new levies which they received, and fresh organization which they acquired during that important period, is a signal proof of the vital importance of fortresses in contributing to national defence. Napoleon has not hesitated to ascribe to the three months thus gained the salvation of France. It is to be constantly recollected that the Republican armies were then totally unable to keep the field; that behind the frontier fortresses there was neither a defensive position, nor a corps to reinforce them; and that if driven from their vicinity, the capital was taken and the war concluded."
In the following year, 1794, when France had completed her vast armaments, and, in her turn, had become the invading power, the enemy had no fortified towns to check the progress of the Republican armies; which, based on strong works of defence, in a few weeks overran Flanders, and drove the allies beyond the Rhine.
In the campaign of 1796, when the army of Moreau had been forced into a precipitate retreat by the admirable strategic operations of the Archduke Charles, the French forces owed their safety to the fortifications on the Rhine. These works arrested the enemy's pursuit and obliged him to resort to the tedious operations of sieges; and the reduction of the French advanced posts alone, Kehl and Huninguen, poorly as they were defended, employed all the resources of the Austrian army, and the skill of their engineers, from early in October till late in February. Kehl was at first assaulted by a force four times as numerous as the garrison; if the enemy had succeeded, he would have cut off Moreau's retreat, and destroyed his army. Fortunately the place was strong enough to resist all assaults; and Moreau, basing himself on the fortresses of Alsace, his right covered by Huninguen, Neuf-Brisach, and Béfort, and his left by the iron barrier of the Netherlands, effectually checked the waves of Austrian success.
Let us now turn to the campaigns of Napoleon. In his first campaign in Italy, 1796, the general was directed "to seize the forts of Savona, compel the senate to furnish him with pecuniary supplies, and to surrender the keys of Gavi, a fortress perched on the rocky height commanding the pass of the Bocchetta." Setting out from Savona, he crossed the mountains at a weak point between the Alps and the Apennines, and succeeded in piercing the enemy's line of defence. The king of Sardinia, jealous of Austrian influence, had refused to permit the Austrian army to garrison his line of fortifications. Napoleon, profiting by his victorious attitude, the mutual jealousy of Austria and Sardinia, and the intrigues of his diplomatists, soon gained possession of these important works. "These Sardinian fortresses," he wrote to the Directory, "at once put the Republicans in possession of the keys of the Peninsula." Basing himself on Coni, Mondovi, Ceva, Gavi, and Alessandria, with Tortosa as his dépôt of magazines, he advanced against Lombardy. Now basing himself on the Adda and Po, with the fortress of Pizzighettone as the dépôt of his magazines, he advanced upon the line of the Adige. Pechiera became his next dépôt, and he now had four fortresses in echelon between him and his first dépôt of magazines; and, after the fall of Mantua, basing himself on the Po, he advanced against the States of the Church, making Ferrara and then Ancona, his places of dépôt.
From the solid basis of the fortresses of Piedmont and Lombardy, "he was enabled to turn his undivided attention to the destruction of the Austrians, and thus commence, with some security, that great career of conquest which he already meditated in the imperial dominions." In this campaign of 1797, after scouring his base, he fortified Palma-Nuova, Osapo, &c., repaired the old fortifications of Klagenfurth, and, as he advanced, established, to use his own words, "a good point d'appui at every five or six marches."
Afterwards, when the Austrians had nearly wrested Italy from the weak grasp of Napoleon's successors, the French saved their army in the fortress of Genoa and behind the line of the Var, which had been fortified with care in 1794–5. Numerous attempts were made to force this line, the advanced post of Fort Montauban being